Photosensitive polyimide precursor and its use for pattern formation

ABSTRACT

A polyimide precursor having repeating units of the formula:                    
     wherein R 1  is a tetravalent organic group having 4 or more carbon atoms; R 2  is a trivalent or tetravalent organic group having one or more aromatic rings; R 3  is a monovalent organic group; A is a monovalent group showing acidity; and n is an integer of 1 or 2, is effective for preparing a highly sensitive negative-working photosensitive material developable with an alkaline aqueous solution in a short time with high resolution.

This application is a divisional of U.S. patent application Ser. No.08/876,240, filed Jun. 16, 1997 now U.S. Pat. No. 6,025,113, the entiredisclosure of which is incorporated herein by reference, which in turnclaims priority of Japenese Patent Application Nos. 08-155324 and09-132353, filed Jun. 17, 1996 and May 27, 1997 respectively.

BACKGROUND OF THE INVENTION

The present invention relates to a photosensitive material suitable forprotective films (e.g. the surface coating films of semiconductordevices), the interlaminar insulating films of thin-film multilayercircuit boards, etc. It relates to, in particular, heat-resistantpolyimides, precursors thereof, photosensitive polyimide precursorcompositions containing the precursors, and negative-workingphotosensitive materials developable with an alkaline aqueous solutionwhich contain the precursors, and a process for forming a resin pattern.

As photosensitive heat-resistant materials for obtaining heat-resistantpolymers, there have been known the materials disclosed in JP-B 5-67026,i.e., the materials obtained by reacting an aromatic tetracarboxylicacid dianhydride with an olefin unsaturated alcohol to synthesize anolefin aromatic tetracarboxylic acid diester, and polymerizing thiscompound and a diamine by dehydrating condensation using a carbodiimide,to introduce thereinto a photosensitive group through a covalent bond;and the materials disclosed in JP-B 63-31939, i.e., the materialsobtained by reacting an aromatic tetracarboxylic acid dianhydride withan aromatic diamine to obtain a poly(amic acid), and reacting thiscompound with an amine compound having a photosensitive group, tointroduce the photosensitive group thereinto through an ionic bond.

In both of these prior art references, a negative relief pattern isobtained by applying a varnish prepared by dissolving the photosensitiveheat-resistant material in a suitable organic solvent on a substrate,drying the varnish to form a coating film, irradiating the film withultraviolet light through a suitable photomask to light-cure the exposedportion, and developing and rinsing the film with organic solvents,respectively.

However, when an organic solvent is used as a developer in patternformation, exposed portion tends to be swollen during development, sothat a pattern is difficult to obtain with high resolution. Moreover,the employment of an organic solvent involves problems such asundesirable influences on the health of workers, much labor required fortreating a waste fluid, etc.

For solving such problems, for example, positive-working polymersobtained by introducing naphthoquinonediazidosulfonylamide groups intothe carboxyl groups of a poly(amic acid) have been proposed as materialsdevelopable with an aqueous liquid (JP-A 6-258835). Since thenaphthoquinonediazidosulfonylamide groups are converted to carboxylgroups by light irradiation, these polymers are characterized in thatthe exposed portion becomes soluble in an alkaline queous solution.Therefore, they are used as positive-working photosensitive materials.

The above-mentioned positive-working photosensitive materials, however,are disadvantageous in that a long time is required for development andthat the sensitivity is not sufficient at a large film thickness (10 μmor more).

SUMMARY OF THE INVENTION

Accordingly, the present invention is intended to remove theabove-mentioned problems and provide a photosensitive material havinghigh resolution and sensitivity which can be rapidly developed with anaqueous solution and is hardly swollen in exposed portion duringdevelopment; a polyimide precursor used in said photosensitive material;and a process for forming a resin pattern using said photosensitivematerial.

The present invention provides a polyimide precursor comprisingrepeating units represented by the following formula (1) and having aweight-average molecular weight of 10,000 to 200,000:

wherein R¹ is a tetravalent organic group containing 4 or more carbonatoms; R² is a trivalent or tetravalent organic group containing atleast one aromatic ring; R³ is a monovalent organic group; A is anacidic monovalent group; and n is 1 or 2.

The present invention also provides the above-mentioned polyimideprecursor which further comprises repeating units represented by theformula:

wherein R¹ is a tetravalent organic group containing 4 or more carbonatoms; R³ is a monovalent organic group; R⁴ is a divalent organic groupcontaining at least one aromatic ring or silicon atom; the number ofrepeating units of the above formula (1) being 10 or more, and thenumber of repeating units of the above formula (2) being 90 or less,when the total number of the repeating units of the formulas (1) and (2)is taken as 100.

The present invention further provides a polyimide obtained from thepolyimide precursor, a polyimide precursor composition and a process forforming a pattern using the polyimide.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a ¹H NMR chart of the polyimide precursor obtained in Example1.

FIG. 2 is a ¹H NMR chart of the polyimide precursor obtained in Example2.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The present invention provides a polyimide precursor soluble in analkaline aqueous solution. The polyimide precursor of the presentinvention comprises repeating units of the following formula (1) and hasa weight-average molecular weight of 10,000 to 200,000, preferably20,000 to 60,000:

wherein R¹ is a tetravalent organic group containing 4 or more carbonatoms; R² is a trivalent or tetravalent organic group containing atleast one aromatic ring; R³ is a monovalent organic group; A is anacidic monovalent group; and n is 1 or 2.

Since this polyimide precursor has one or two acidic groups A in thestructural unit of polymer, the polyimide precursor before curing ishighly soluble in an alkaline aqueous solution. Therefore, such apolyimide precursor can easily be developed with an alkaline aqueoussolution and hence can remove the above-mentioned various disadvantagesof the employment of an organic solvent as a developer.

When a photosensitive group is used as R³, the polyimide precursor canbe obtained as a negative-working photosensitive polyimide precursorwhich is cured by exposure to light. When R³ is a photosensitive group,the photosensitive group is introduced through an ester linkage, so thatthe curing property of exposed portion and the sensitivity are excellenteven in the case of a thick film (10 μm or more). Therefore, ofpolyimide precursors of the above formula (1), those in which R³ is aphotosensitive group are characterized in that they are soluble in analkaline aqueous solution but are cured by exposure to light to becomeinsoluble in the alkaline aqueous solution. Accordingly, they areespecially suitable for the photosensitive material of the presentinvention. When such a polyimide precursor is used, a negative patterncan be formed in a short development time. Thus, the present inventionprovides a negative-working photosensitive material characterized bycontaining a photosensitive polyimide precursor which is soluble in analkaline aqueous solution but is cured by exposure to light to becomeinsoluble in the alkaline aqueous solution.

Said polyimide precursor need not have acidic groups A in all therepeating units and it is sufficient that 10 mol % or more of therepeating units contain acidic groups A. That is, as the polyimideprecursor of the present invention, there can also be used polyimideprecursors which further comprise repeating units of the followingformula (2) in addition to the repeating units of the above formula (1),and in which the number of repeating units of the above formula (1) isnot more than 100 and not less than 10 and the number of repeating unitsof the formula (2) is not more than 90 and not less than 0, when thetotal number of the repeating units of the formulas (1) and (2) is takenas 100:

wherein R¹ is a tetravalent organic group containing 4 or more carbonatoms; R³ is a monovalent organic group; R⁴ is a divalent organic groupcontaining at least one aromatic ring or silicon atom.

The polyimide precursor of the present invention can be obtained, forexample, by reacting a carboxylic acid halide such as an acid chlorideof the following formula (12) with a diamine of the following formula(13) in a solvent:

(R³OCO)₂R¹(COCl)₂  (12)

AnR²(NH₂)₂  (13)

The proportion of the diamine of the above formula (13) may be 10 mol %or more based on the total number of mols of diamine components used.That is, the polyimide precursor of the present invention can beobtained also by copolymerizing an acid chloride of the above formula(12) with a mixture of 90 mol % or less of a diamine of the followingformula (14) and 10 mol % or more of a diamine of the above formula(13):

R⁴(NH₂)₂  (14)

The present invention also provides a photosensitive material and apolyimide precursor composition which contain the polyimide precursor ofthe present invention. The polyimide precursor composition of thepresent invention preferably contains a siloxane-containing poly(amicacid) comprising repeating units of any of the following formulas (24)in addition to the above-mentioned polyimide precursor of the formula(1), for the improvement of the adhesive properties to a substrate, inparticular, a silicon wafer during development and after curing:

wherein R¹ is a tetravalent organic group containing 4 or more carbonatoms; R¹³ is a divalent organic group containing at least one aromaticring; R¹¹ is a tetravalent organic group having at least one siloxaneskeleton; and R¹² is a divalent organic group having at least onesiloxane skeleton.

The siloxane-containing poly(amic acid) need not contain siloxaneskeletons in all the repeating units and it is sufficient that 1 mol %or more of the repeating units contain siloxane skeletons. That is, thefollowing poly(amic acid)s are also effective in improving the adhesiveproperties of the polyimide precursor composition: poly(amic acid)swhich further comprise repeating units of the following formula (25) inaddition to repeating unit of any of the above formulas (24):

wherein R¹ is a tetravalent organic group containing 4 or more carbonatoms; and R¹³ is a divalent organic group containing at least onearomatic ring, the number of repeating units of any of the aboveformulas (24) being 1 or more, and the number of repeating units of theabove formula (25) being 99 or less, when the total number of therepeating units of any of the formulas (24) and the repeating units ofthe formula (25) is taken as 100.

As a process for forming a resin pattern using the photosensitivepolyimide precursor of the present invention, the present inventionfurther provides a process for forming a resin pattern which comprises astep of irradiating a coating film made of a photosensitive polyimideprecursor composition containing the photosensitive polyimide precursorof the present invention, with light through a mask having apredetermined pattern, and a step of developing the coating film with analkaline aqueous solution.

The present invention still further provides a polyimide comprising inthe molecule 10 mol % or more of repeating units of the formula (10)shown below, as a polyimide obtained by heating and curing a polyimideprecursor composition containing the polyimide precursor of the presentinvention. The weight-average molecular weight of the polyimide of thepresent invention is 10,000 to 200,000, preferably 20,000 to 60,000. Thepolyimide of the present invention can easily be obtained in the form ofa film of a complicated shape by use of the polyimide precursor of thepresent invention and hence is suitable for the protective film of asemiconductor device, etc.

wherein R¹ is a tetravalent organic group containing 4 or more carbonatoms; R² is a trivalent or tetravalent organic group containing atleast one aromatic ring; R³ is a monovalent organic group; A is anacidic monovalent group; and n is 1 or 2.

The polyimide of the present invention may further comprise in themolecule 90 mol % or less of repeating units of the formula (11) shownbelow. That is, in the polyimide of the present invention, the number ofrepeating units of the above formula (10) is not more than 100 and notless than 10 and the number of repeating units of the above formula (11)is not more than 90 and not less than 0, when the total number of therepeating units of the formulas (10) and (11) in the molecule is takenas 100:

wherein R¹ is a tetravalent organic group containing 4 or more carbonatoms; and R⁴ is a divalent organic group containing at least onearomatic ring or silicon atom.

Polyimides in which 1 to 30 mol % of the groups R¹ and/or groups R⁴ inthe molecule contain at least one siloxane skeleton are especiallypreferable because of their excellent adhesive properties to asubstrate. For example, polyimides in which 1 to 30 mol % of the groupsR⁴ are groups represented by the following formula (35) are suitable forthe surface protective film of a semiconductor device, the interlaminarinsulating film of a thin-film multilayer circuit board, etc.:

As described above, the polyimide precursor of the present invention issoluble in an alkaline aqueous solution because of its acidic groups Ain the molecule. Although the acidic group A is preferably any of thesubstituents of the formulas (15) shown below, any acidic group otherthan these susbstituents may be used as the acidic group A. All theacidic groups A in the molecule may be the same, or different groups maybe present in the molecule as the acidic groups A. Of the acidic groupsof the formula (15) exemplified below, carboxyl group and hydroxyl groupare especially preferable because of ease of synthesis.

The diamine residue R² to which the acidic group A is bonded is atrivalent or tetravalent organic group containing at least one aromaticring, from the viewpoint of the mechanical properties, heat resistanceand adhesive properties of a polyimide film obtained by curing.Preferable examples of the organic group R² are those represented by aseries of the formulas (4) shown below. All the organic groups R² in themolecule may be the same, or different groups may be present in themolecule as the organic groups R².

wherein Z is a group selected from the group consisting of —O—, —S—,—CO—, —SO₂—, —CH₂—, —C(CF₃)₂—,

The diamine residue R⁴ of the repeating unit of the formula (2)containing no acidic group A is a divalent organic group containing atleast one aromatic ring and/or at least one silicon atom, from theviewpoint of the mechanical properties, heat resistance and adhesiveproperties of a polyimide film obtained by curing. Preferable examplesof the organic group R⁴ are those represented by a series of theformulas (7), (8) and (9) shown below. All the organic groups R4 in themolecule may be the same, or different groups may be present in themolecule as the organic groups R⁴.

In the repeating units of the formulas (1) and (2) of the polyimideprecursor of the present invention, R¹ is a tetravalent organic groupcontaining 4 or more carbon atoms, from the viewpoint of the mechanicalproperties, heat resistance and adhesive properties of a polyimide filmobtained by curing. Preferable examples of the organic group R¹ arethose represented by a series of the formulas (3) shown below. All theorganic groups R¹ in the molecule may be the same, or different groupsmay be present in the molecule as the organic groups R¹. Of the organicgroups exemplified below, those having a biphenyl skeleton or adiphenylsulfone skeleton are preferable because when a pattern is formedusing the photosensitive polyimide precursor containing such organicgroups, the profile of the pattern is satisfactory.

In the repeating units of the formulas (1) and (2) of the polyimideprecursor of the present invention, R³ is a monovalent organic group. Inthe polyimide precursor of the present invention, the linkage of R³ tocarboxyl group is an ester linkage and is advantageous in that it isstronger than ionic bond and is not severed even by dissolution in asolvent.

All the organic groups R³ in the molecule may be the same, or differentgroups may be present in the molecule as the organic groups R³. When 10mol % or more of the organic groups R3 in the molecule arephotosensitive groups (e.g. groups removable by light irradiation),photosensitivity can be desirably imparted to the polyimide precursor.Examples of the photosensitive group are organic groups represented bythe following formula (5), and two or more kinds of groups representedby the formula (5) may be present in the molecule:

wherein R⁵, R⁶ and R⁷ are independently a group selected from the groupconsisting of hydrogen, alkyl groups, phenyl group, vinyl group andpropenyl group; and R8 is a divalent organic group.

The groups represented by the formula (5) are preferable because theyimpart a high photosensitivity to the polyimide precursor. Inparticular, organic groups represented by the following formula (6) arepreferable in the present invention because they realize a highsensitivity and moreover permit easy synthesis:

When some (preferably 10 mol % or more) of the groups R³ are groupsrepresented by the general formula (5), the remaining groups R³ (i.e.preferably 0 to 90 mol %) are preferably alkyl groups having 6 or lesscarbon atoms. As the alkyl group, a methyl group, an ethyl group, ann-propyl group, an isopropyl group and an n-butyl group are especiallysuitable from the view-point of the film properties of a polyimideobtained by curing the polyimide precursor.

As described above, the polyimide precursor of the present invention isused as a starting material for a negative-working photosensitivematerial the light exposed portion of which are cured. There areexplained below components other than the polyimide precursor of thephotosensitive polyimide precursor composition containing the polyimideprecursor of the present invention.

The polyimide precursor composition of the present invention preferablycontains a poly(amic acid) having siloxane skeletons and comprisingrepeating units represented by any of the above formulas (24). Thissiloxane-containing poly(amic acid) is effective in maintaining adhesiveproperties to a silicon wafer substrate after curing, in particular,high adhesive properties even after PCT (pressure cooker test)treatment. The poly(amic acid) having siloxane skeletons can besynthesized from an acid dianhydride and a diamine one or both of whichhave at least one siloxane skeleton. In the present invention, asiloxane-containing poly(amic acid) having a weight-average molecularweight of 10,000 to 200,000 is usually used.

The proportion of the siloxane-containing poly(amic acid) in thepolyimide precursor composition of the present invention is preferably 1to 30 parts by weight per 70 to 99 parts by weight of the polyimideprecursor comprising repeating units of the above formula (1) (namely,containing acidic groups A), in order to improve the adhesive propertiesand not to impair the developability.

In the formulas (24) and the formula (25), R¹ is as defined in the aboveformula (1) and formula (2).

In the formulas (24), R¹¹ is a tetravalent organic group having at leastone siloxane skeleton. From the viewpoint of the mechanical properties,heat resistance and adhesive properties of a polyimide film obtained bycuring, preferable examples of the organic group R¹¹ are thoserepresented by a series of the formulas (26) shown below. All theorganic groups R¹¹ in the molecule may be the same, or different groupsmay be present in the molecule as the organic groups R¹¹.

In the formulas (24), R¹² is a divalent organic group having at leastone siloxane skeleton. From the viewpoint of the mechanical properties,heat resistance and adhesive properties of a polyimide film obtained bycuring, preferable examples of the organic group R¹² are thoserepresented by a series of the formulas (27) shown below. All theorganic groups R¹² in the molecule may be the same, or different groupsmay be present in the molecule as the organic groups R¹².

wherein n is an integer of 2 to 12.

In the formulas (24) and the formula (25), the diamine residue R¹³ is adivalent organic group containing at least one aromatic ring, from theviewpoint of the mechanical properties, heat resistance and adhesiveproperties of a polyimide film obtained by curing. Preferable examplesof the organic group R¹³ are those represented by the above formulas (7)and formulas (9) and a series of the formulas (36) shown below. All theorganic groups R¹³ in the molecule may be the same, or different groupsmay be present in the molecule as the organic groups R¹³.

For attaining a practical photosensitivity, the photosensitive polyimideprecursor composition of the present invention preferably contains atleast one photosensitizer. Preferable examples of the photosensitizerare Michler's ketone, bis-4,4′-diethylaminobenzophenone, benzophenone,3,5-bis(diethylaminobenzylidene)-N-methyl-4-piperidone,3,5-bis(dimethylaminobenzylidene)-N-methyl-4-piperidone,3,5-bis(diethylaminobenzylidene)-N-ethyl-4-piperidone,3,3′-carbonylbis(7-diethylamino)coumarin, riboflavin tetrabutyrate,2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one,2,4-dimethylthioxanthone, 2,4-diethylthioxanthone,2,4-diisopropylthioxanthone, 3,5-dimethylthioxanthone,3,5-diisopropylthioxanthone,1-phenyl-2-(ethoxycarbonyl)oxyiminopropan-1-one, benzoin ether, benzoinisopropyl ether, benzanthrone, 5-nitroacenaphthene, 2-nitrofluorene,anthrone, 1,2-benzanthraquinone, 1-phenyl-5-mercapto-1H-tetrazole,thioxanthen-9-one, 10-thioxanthenone, 3-acetylindole,2,6-di(p-dimethylaminobenzal)-4-carboxycyclohexanone,2,6-di(p-dimethylaminobenzal)-4-hydroxycyclohexanone,2,6-di(p-diethylaminobenzal)-4-carboxycyclohexanone,2,6-di(p-diethylaminobenzal)-4-hydroxycyclohexanone,4,6-dimethyl-7-ethylaminocoumarin, 7-diethylamino-7-methylcoumarin,7-diethylamino-3-(1-methylbenzoimidazolyl)coumarin,3-(2-benzoimidazolyl)-7-diethylaminocoumarin,3-(2-benzothiazolyl)-7-diethylaminocoumarin,2-(p-dimethylaminostyryl)benzoxazole,2-(p-dimethylaminostyryl)quinoline, 4-(p-dimethylaminostyryl)quinoline,2-(p-dimethylaminostyryl)benzothiazole,2-(p-dimethylaminostyryl)-3,3-dimethyl-3H-indole, etc. Thephotosensitizer is not limited to them.

The photosensitizer(s) is blended in an amount of preferably 0.1 to 50parts by weight, more preferably 0.3 to 20 parts by weight, per 100parts by weight of the polyimide precursor of the present invention.When the amount is outside the range of 0.1 to 50 parts by weight, nosensitizing effect can be obtained in some cases or an undesirableinfluence on the developability is brought about in some cases. As thephotosensitizer(s), either one compound or a mixture of severalcompounds may be used.

For attaining a practical photosensitivity, the photosensitive polyimideprecursor composition of the present invention preferably contains atleast one photopolymerization assistant (or auxiliary agent). As thephotopolymerization assistant, there can be used, for example,4-diethylaminoethyl benzoate, 4-dimethylaminoethyl benzoate,4-diethylaminopropyl benzoate, 4-dimethylaminopropyl benzoate,4-dimethylaminoisoamyl benzoate, N-phenylglycine,N-methyl-N-phenylglycine, N-(4-cyanophenyl)glycine,4-dimethylaminobenzonitrile, ethylene glycol dithioglycolate, ethyleneglycol di(3-mercaptopropionate), trimethylolpropane thioglycolate,trimethylolpropane (3-mercaptopropionate), pentaerythritoltetrathioglycolate, pentaerythritol tetra(3-mercaptopropionate),trimethylolethane trithioglycolate, trimethylolpropane trithioglycolate,trimethylolethane tri(3-mercaptopropionate), dipentaerythritolhexa(3-mercaptopropionate), thioglycolic acid, α-mercaptopropionic acid,t-butyl peroxybenzoate, t-butyl peroxymethoxybenzoate, t-butylperoxynitrobenzoate, t-butyl peroxyethylbenzoate, phenylisopropylperoxybenzoate, di-t-butyl dibenzyloxyisophthalate, tri-t-butyltriperoxytrimelitate, tri-t-butyl triperoxytrimesitate, tetra-t-butyltetraperoxypyromellitate, 2,5-dimethyl-2,5-di(benzoylperoxy)hexane,3,3′,4,4′-tetra(t-butylperoxycarbonyl)benzophenone,3,3′,4,4′-tetra(t-amylperoxycarbonyl)benzophenone,3,3′,4,4′-tetra(t-hexylperoxycarbonyl)benzophenone,2,6-di(p-azidobenzal)-4-hydroxycyclohexanone,2,6-di(p-azidobenzal)-4-carboxycyclohexanone,2,6-di(p-azidobenzal)-4-methoxycyclohexanone,2,6-di(p-azidobenzal)-4-hydroxymethylcyclohexanone,3,5-di(p-azidobenzal)-1-methyl-4-piperidone,3,5-di(p-azidobenzal)-4-piperidone,3,5-di(p-azidobenzal)-N-acetyl-4-piperidone,3,5-di(p-azidobenzal)-N-methoxycarbonyl-4-piperidone,2,6-di(m-azidobenzal)-4-hydroxycyclohexanone,2,6-di(m-azidobenzal)-4-carboxycyclohexanone,2,6-di(m-azidobenzal)-4-methoxycyclohexanone,2,6-di(m-azidobenzal)-4-hydroxymethylcyclohexanone,3,5-di(m-azidobenzal)-N-methyl-4-piperidone,3,5-di(m-azidobenzal)-4-piperidone,3,5-di(m-azidobenzal)-N-acetyl-4-piperidone,3,5-di(m-azidobenzal)-N-methoxycarbonyl-4-piperidone,2,6-di(p-azidocinnamylidene)-4-hydroxycyclohexanone,2,6-di(p-azidocinnamylidene)-4-carboxycyclohexanone,2,6-di(p-azidocinnamylidene)-4-hydroxymethylcyclohexanone,3,5-di(p-azidocinnamylidene)-N-methyl-4-piperidone,4,4′-diazidochalcone, 3,3′-diazidochalcone, 3,4′-diazidochalcone,4,3′-diazidochalcone,1,3-diphenyl-1,2,3-propanetrione-2-(o-acetyl)oxime,1,3-diphenyl-1,2,3-propanetrione-2-(o-n-propylcarbonyl)oxime,1,3-diphenyl-1,2,3-propanetrione-2-(o-methoxycarbonyl)oxime,1,3-diphenyl-1,2,3-propanetrione-2-(o-ethoxycarbonyl)oxime,1,3-diphenyl-1,2,3-propanetrione-2-(o-benzoyl)oxime,1,3-diphenyl-1,2,3-propanetrione-2-(o-phenyloxycarbonyl)oxime,1,3-bis(p-methylphenyl)-1,2,3-propanetrione-2-(o-benzoyl)oxime,1,3-bis(p-methoxyphenyl)-1,2,3-propanetrione-2-(o-ethoxycarbonyl)oxime,1-(p-methoxyphenyl)-3-(p-nitrophenyl)-1,2,3-propanetrione-2-(o-phenyloxycarbonyl)oxime,etc. The photopolymerization assistant is not limited to them.

The photopolymerization assistant(s) is blended in an amount ofpreferably 0.1 to 50 parts by weight, more preferably 0.3 to 20 parts byweight, per 100 parts by weight of the polyimide precursor of thepresent invention. When the amount is outside the range of 0.1 to 50parts by weight, no sensitizing effect can be obtained in some cases oran undesirable influence on the developability is brought about in somecases. As the photopolymerization assistant(s), either one compound or amixture of several compounds may be used.

For attaining a practical photosensitivity, the photosensitive polyimideprecursor composition of the present invention may futher contain atleast one comonomer in addition to the above-mentionedphotosensitizer(s) and photopolymerization assistant(s). The comonomeris a compound having a carbon-carbon double bond and facilitates thephotopolymerization. Preferable examples of the comonomer are1,6-hexanediol diacrylate, neopentylglycol diacrylate, ethylene glycoldiacrylate, pentaerythritol diacrylate, trimethylolpropane triacrylate,pentaerythritol triacrylate, dipentaerythritol hexaacrylate,tetramethylolpropane tetraacrylate, tetraethylene glycol diacrylate,1,6-hexanediol dimethacrylate, neopentylglycol dimethacrylate, ethyleneglycol dimethacrylate, pentaerythritol dimethacrylate,trimethylolpropane trimethacrylate, pentaerythritol trimethacrylate,dipentaerythritol hexamethacrylate, tetramethylolpropanetetramethacrylate, tetraethylene glycol dimethacrylate, etc. Thecomonomer is not limited to them.

The comonomer(s) is blended in an amount of preferably 1 to 100 parts byweight, more preferably 3 to 50 parts by weight, per 100 parts by weightof the polyimide precursor of the present invention. When the amount isoutside the range of 1 to 100 parts by weight, no desired effect can beobtained in some cases or an undesirable influence on the developabilityis brought about in some cases. As the comonomer(s), either one compoundor a mixture of several compounds may be used.

The photosensitive polyimide precursor composition of the presentinvention may contain a suitable organic solvent. When the compositionis in the form of a solution in the suitable solvent, it can be used asa varnish and is hence convenient when formed into a film. As thesolvent, aprotic polar solvents are preferable from the viewpoint ofsolubility. Specific preferable examples of the solvent areN-methyl-2-pyrrolidone, N-acetyl-2-pyrrolidone, N-benzyl-2-pyrrolidone,N,N-dimethylformamide, N,N-dimethylacetamide, dimethyl sulfoxide,hexamethylphosphoric triamide, N-acetyl-ε-caprolactam,dimethylimidazolidinone, diethylene glycol dimethyl ether, triethyleneglycol dimethyl ether, γ-butyrolactone, etc. These may be used singly oras a mixture thereof. The organic solvent may be either a solvent leftas it is after being used for the synthesis of the polyimide precursor,or a solvent freshly added to the polyimide precursor isolated. Forimproving the coating properties, a solvent such as toluene, xylene,diethyl ketone, methoxybenzene, cyclopentanone or the like may beincorporated into the composition so long as it has no undesirableinfluence on the solubility of the polymer. Particularly whencyclopentanone is used as the solvent, a photosensitive polyimideprecursor composition excellent in coating properties for a siliconwafer can be obtained.

The process for forming a resin pattern of the present inventioncomprises forming a polyimide film composed of a cured product of thephotosensitive polyimide precursor of the present invention, by aphotolithographic technique.

In the formation process of a resin pattern of the present invention, acoating film of the photosensitive polyimide precursor composition ofthe present invention is formed on the surface of a substrate at first.In this formation process, the substrate surface may be previouslytreated with an adhesion assistant in order to improve the adhesionstrength between the substrate and the coating film or a polyimide filmobtained by curing by heating. It is also possible to add an adhesionassistant to a varnish of the photosensitive polyimide precursorcomposition previously.

The coating film of the photosensitive polyimide precursor compositionis formed, for example, by forming a film of a varnish of thephotosensitive polyimide precursor composition, and drying this film.The film of the varnish is formed by a means properly selected frommeans such as spin-coating using a spinner, immersion, spray printing,screen printing, etc., depending on the viscosity of the varnish, etc.The thickness of the coating film can be adjusted by the coatingconditions, the solid concentration in the composition, etc. Theabove-mentioned coating film may be obtained by forming a coating filmof the polyimide precursor composition on a support previously,preparing a sheet of the composition by peeling the coating film fromthe support, and attaching this sheet to the surface of theabove-mentioned substrate.

Then, the coating film is irradiated with light (usually ultravioletlight) through a photomask having a predetermined pattern, after whichthe non-exposed portion is dissolved away with an alkaline aqueoussolution to obtain a desired relief pattern. This developing step may becarried out using a conventional positive type photoresist developingapparatus.

In the formation process of a resist pattern of the present invention,an alkaline aqueous solution is used as a developing solution. Thedeveloping solution may be either an aqueous solution of one compound oran aqueous solution of two or more compounds so long as it is alkaline.The alkaline aqueous solution is usually a solution prepared bydissolving one or more basic compounds in water. Although theconcentration of the basic compound(s) is usually 0.1 to 50 wt/wt %, itis preferably 0.1 to 30 wt/wt % in view of influences on the substrate,etc. For improving the solubility of the polyimide precursor, thedeveloping solution may further contain water-soluble organic solventssuch as methanol, ethanol, propanol, isopropanol,N-methyl-2-pyrrolidone, N,N-dimethylformamide, N,N-dimethylacetamide,etc.

The aforesaid basic compounds include, for example, hydroxides orcarbonates of alkali metals, alkaline earth metals or ammonium ion, andamine compounds. Specific preferable examples of the basic compounds are2-dimethylaminoethanol, 3-dimethylamino-1-propanol,4-dimethylamino-1-butanol, 5-dimethylamino-1-pentanol,6-dimethylamino-1-hexanol, 2-dimethylamino-2-methyl-1-propanol,3-dimethylamino-2,2-dimethyl-1-propanol, 2-diethylaminoethanol,3-diethylamino-1-propanol, 2-diisopropylaminoethanol,2-di-n-butylaminoethanol, N,N-dibenzyl-2-aminoethanol,2-(2-dimethylaminoethoxy)ethanol, 2-(2-diethylaminoethoxy)ethanol,1-dimethylamino-2-propanol, 1-diethylamino-2-propanol,N-methyldiethanolamine, N-ethyldiethanolamine, N-n-butyldiethanolamine,N-t-butyldiethanolamine, N-lauryldiethanolamine,3-diethylamino-1,2-propanediol, triethanolamine, triisopropanolamine,N-methylethanolamine, N-ethylethanolamine, N-n-butylethanolamine,N-t-butylethanolamine, diethanolamine, diisopropanolamine,2-aminoethanol, 3-amino-1-propanol, 4-amino-1-butanol,6-amino-1-hexanol, 1-amino-2-propanol, 2-amino-2,2-dimethyl-1-propanol,1-aminobutanol, 2-amino-1-butanol, N-(2-aminoethyl)ethanolamine,2-amino-2-methyl-1,3-propanediol, 2-amino-2-ethyl-1,3-propanediol,3-amino-1,2-propanediol, 2-amino-2-hydroxymethyl-1,3-propanediol, sodiumhydroxide, potassium hydroxide, ammonium hydroxide, sodium carbonate,potassium carbonate, ammonium carbonate, sodium hydrogencarbonate,potassium hydrogencarbonate, ammonium hydrogencarbonate,tetramethylammonium hydroxide, tetraethylammonium hydroxide,tetrapropylammonium hydroxide, tetraisopropylammonium hydroxide,aminomethanol, 2-aminoethanol, 3-aminopropanol, 2-aminopropanol,methylamine, ethylamine, propylamine, isopropylamine, dimethylamine,diethylamine, dipropylamine, diisopropylamine, trimethylamine,triethylamine, tripropylamine, triisopropylamine, etc. Any compoundother than those exemplified above may be used so long as it iswater-soluble and its aqueous solution is alkaline.

The relief pattern formed by the development is then washed with arinsing liquid to be freed of the developing solution. Preferableexamples of the rinsing liquid are methanol, ethanol, isopropanol,water, etc. which are sufficiently miscible with the developingsolution.

The relief pattern obtained by the above-mentioned treatment isheat-treated at a temperature chosen in the range of 150° C. to 450° C.,whereby a resist pattern made of the polyimide of the present inventioncan be obtained with high resolution. This resist pattern has a highheat resistance and excellent mechanical properties.

The present invention is illustrated by way of the following Examples.

EXAMPLE 1

A. Synthesis of a Polyimide Precursor

(1) Synthesis of an Acid Chloride

When 9.42 g (0.032 mol) of 3,3′,4,4′-biphenyl-tetracarboxylicdianhydride (BPDA), 8.32 g (0.064 mol) of 2-hydroxyethyl methacrylate(HEMA), 5.06 g (0.064 mol) of pyridine, 0.03 g of t-butylcatechol and 70ml of N-methyl-2-pyrrolidone (NMP) were placed in a 200-mlfour-neckedflask and stirred at 60° C., a transparent solution was obtained in 2hours. This solution was then stirred at room temperature for 7 hours,after which 9.88 g (0.083 mol) of thionyl chloride was added dropwiseover a period of 10 minutes while cooling the flask with ice. Theresulting mixture was stirred at room temperature for 1 hour to obtain asolution containing an acid chloride.

(2) Synthesis of a Polyimide Precursor [a Poly(amic acid)ester]

In another 200-ml four-necked flask were placed 4.72 g (0.031 mol) of3,5-diaminobenzoic acid, 5.06 g (0.064 mol) of pyridine, 0.03 g oft-butylcatechol and 50 ml of N-methyl-2-pyrrolidone (NMP), after whichthe acid chloride solution obtained in section (1) above was slowlydropped in the flask with stirring over a period of 1 hour while coolingthe flask with ice (while maintaining the temperature at 10° C. orlower). The resulting mixture was stirred at room temperature for 1 hourand poured into 1 liter of water, and the polymer precipitated wascollected by filtration, washed twice with water and then dried in vacuoto obtain 22 g of a poly(amic acid) ester comprising repeating units ofthe formula (16) shown below. The weight-average molecular weight of thepoly(amic acid) ester was measured by GPC (gel permeationchromatography) and found to be 44,000 in terms of polystyrene.

H¹-NMR (proton nuclear magnetic resonance) spectrum of the obtainedpolyimide precursor was measured to obtain peaks at 1.82 ppm (s, 6H,—CH3), 4.37-4.51 ppm (d, 8H, —CH₂—), 5.59-5.98 ppm (d, 4H, ═CH₂),7.84-8.38 ppm (m, 9H, aromatic ring) and 10.79 ppm (s, 2H, —NH—). In themeasurement, dimethyl sulfoxide-d₆ was used as a solvent. The chartobtained is shown in FIG. 1. In the chart, it can be speculated that thepeaks at 2.15 ppm and 2.67 ppm are due to the remaining solvent forsynthesis (NMP) and the peak at 3.27 ppm due to water as a contaminant.

B. Preparation of a Polyimide Precursor Composition

In a mixture of 15.0 g of γ-butyrolactone and 7.5 g ofN,N-dimethylacetamide were dissolved 10 g of the obtained polymer andthen 100 mg of3,5-bis(4-diethylaminobenzylidene)-1-methyl-4-azacyclohexanone and 200mg of 4-diethylaminoethyl benzoate, and the resulting solution wasfiltered through a-filter with a pore size of 5 μm under pressure toobtain a photosensitive polyimide precursor composition in the form of asolution.

C. Evaluation of a Polyimide Film

The obtained solution was spin-coated on a silicon wafer with a spinnerand then dried on a hot plate of 90° C. for 3 minutes to obtain acoating film in 15 μm thickness. The coating film was exposed to lightfrom a 500-W high pressure mercury arc lamp at an exposure dose of 200mJ/cm2 (ultraviolet light intensity at 365 nm), developed by immersionin a 2.38 wt % aqueous tetramethylammonium hydroxide solution (adeveloping solution) of 20° C. for 1 minute, and then rinsed with waterto obtain a semi-cured polyimide precursor film.

This film was cured by heating at 200° C. for 30 minutes and then at400° C. for 60 minutes, to obtain a film of 10 μm thickness made of apolyimide comprising repeating units of the following formula (17):

This polyimide film was peeled from the silicon wafer and its elongationwas measured and found to be as good as 9%. The dependence of the filmthickness after the development on the exposure dose was measured tofind that the sensitivity was 80 mJ/cm² when the sensitivity was definedas an exposure dose at which the film thickness after the developmentbecame one-half of the coating thickness.

When a polyimide film of 2 to 3 μm thick was formed and its infraredabsorption spectrum was measured, there were observed an absorption dueto imide group at 1780 cm⁻¹ and an absorption due to carboxyl group at2800 to 3600 cm⁻¹.

D. Formation of a Resin Pattern

The polyimide precursor composition prepared in step B was coated,exposed, developed and then rinsed in the same manner as described inthe above-mentioned polyimide film formation, except that in theexposure, the coating film was closely covered with a photomaskpatterned with stripes of 10 μm wide. Thus, there was obtained a reliefpattern of 10 μm wide made of semi-cured polyimide precursor and havingsharp edge faces. This pattern was heat-treated in the same manner as inthe above-mentioned polyimide film formation to obtain a resin patternmade of polyimide.

EXAMPLE 2

A. Synthesis of a Polyimide Precursor

(1) Synthesis of an Acid Chloride

When 10.00 g (0.032 mol) of 4,4′-oxydiphthalic dianhydride (ODPA), 8.32g (0.064 mol) of 2-hydroxyethyl methacrylate (HEMA), 5.06 g (0.064 mol)of pyridine, 0.03 g of t-butylcatechol and 70 ml ofN-methyl-2-pyrrolidone (NMP) were placed in a 200-ml four-necked flaskand stirred at 60° C., a transparent solution was obtained in 30minutes. This solution was then stirred at room temperature for 6 hours,after which 9.88 g (0.083 mol: 1.3 equivalents) of thionyl chloride wasadded dropwise over a period of 10 minutes while cooling the flask withice. The resulting mixture was stirred at room temperature for 1 hour toobtain an acid chloride solution.

(2) Synthesis of a Polyimide Precursor [a Poly(amic acid)ester]

In another 200-ml four-necked flask were placed 4.72 g (0.031 mol) of3,5-diaminobenzoic acid, 5.06 g (0.064 mol) of pyridine, 0.03 g oft-butylcatechol and 50 ml of N-methyl-2-pyrrolidone (NMP), after whichthe acid chloride solution obtained in section (1) above was slowlydropped in the flask with stirring over a period of 1 hour while coolingthe flask with ice (while maintaining the temperature at 10° C. orlower). The resulting mixture was stirred at room temperature for 1 hourand poured into 1 liter of water, and the polymer precipitated wascollected by filtration, washed twice with water and then dried in vacuoto obtain 20 g of a poly(amic acid) ester comprising repeating units ofthe formula (18) shown below. The weight-average molecular weight ofthis polymer was measured by GPC (gel permeation chromatography) andfound to be 39,000 in terms of polystyrene.

H¹-NMR (proton nuclear magnetic resonance) spectrum of the obtainedpolyimide precursor was measured to obtain peaks at 1.79 ppm (s, 6H,—CH₃), 4.32-4.45 ppm (d, 8H, —CH₂—), 5.56-5.94 ppm (d, 4H, ═CH₂),7.30-8.32 ppm (m, 9H, aromatic ring) and 10.69 ppm (s, 2H, —NH—). In themeasurement, dimethyl sulfoxide-d₆ was used as a solvent. The chartobtained is shown in FIG. 2. In the chart, it can be speculated that thepeaks at 2.15 ppm and 2.67 ppm are due to the remaining solvent forsynthesis (NMP) and the peak at 3.27 ppm due to water as a contaminant.

B. Preparation of a Photosensitive Polyimide Precursor Composition

In a mixture of 15.0 g of γ-butyrolactone and 7.5 g ofN,N-dimethylacetamide were dissolved 10 g of the obtained polymer andthen 100 mg of Michler's ketone and 200 mg of1,3-diphenyl-1,2,3-propanetrione-2-(o-ethoxycarbonyl)oxime, and theresulting solution was filtered through a filter with a pore size of 5μm under pressure to obtain a photosensitive polyimide precursorcomposition in the form of a solution.

C. Evaluation of a Polyimide Film

The obtained solution was spin-coated on a silicon wafer with a spinnerand then dried on a hot plate of 90° C. for 3 minutes to obtain acoating film of 15 μm thick. The coating film was exposed to light froma 500-W high pressure mercury arc lamp at an exposure dose of 200 mJ/cm2(ultraviolet light intensity at 365 nm). After the exposure, the coatingfilm was developed by immersion in a 2.38 wt % aqueoustetramethylammonium hydroxide solution (a developing solution) of 20° C.for 1 minute and then rinsed with water to obtain a semi-cured polyimideprecursor film.

This film was cured by heating at 200° C. for 30 minutes and then at400° C. for 60 minutes, to obtain a film of 10 μm thick made of apolyimide comprising repeating units of the following formula (19):

This polyimide film was peeled from the silicon wafer and its elongationwas measured and found to be as good as 10%. The dependence of the filmthickness after the development on the exposure dose was measured tofind that the sensitivity was 90 mJ/cm² when the sensitivity was definedas an exposure dose at which the film thickness after the developmentbecame one-half of the coating thickness.

When a polyimide film of 2 to 3 μm thick was formed and its infraredabsorption spectrum was measured, there were observed an absorption dueto imide group at 1785 cm⁻¹ and an absorption due to carboxyl group at2800 to 3600 cm⁻¹.

D. Formation of a Resin Pattern

The polyimide precursor composition prepared in step B was coated,exposed, developed and then rinsed in the same manner as described inthe formation of the polyimide film in step C in this Example, exceptthat in the exposure, the coating film was closely covered with aphotomask patterned with stripes of 10 μm wide. Thus, there was obtaineda relief pattern of 10 μm wide made of semi-cured polyimide precursorand having sharp edge faces. This pattern was heat-treated in the samemanner as in the above-mentioned polyimide film formation to obtain aresin pattern made of polyimide, with high precision.

EXAMPLES 3 TO 10

Acid chlorides of tetracarboxylic acid diesters were synthesized in thesame manner as described in Example 1 except for using the aciddianhydride and OH component (alcohol) listed in Table 1 and Table 2.Polyimide precursors were synthesized by reacting each acid chloridewith the diamines listed in Table 1 and Table 2 under the same reactionconditions as described in Example 1. The weight-average molecularweights of the obtained polyimide precursors were 20,000 to 40,000. Therepeating units of the polyimide precursors are shown in Table 3 andTable 4.

TABLE 1 Compositios of photosensitive polyimide precursors Aciddianhydride Diamine OH component Example (molar ratio) (molar ratio)(molar ratio) 3 3,3′,4,4′- 3,5-Diaminobenzoic 2-Hydroxy- Biphenyl- acidethyl methacrylate tetracarboxylic (50) (200) dianhydride 4,4′-Diamino-(100) diphenyl ether (50) 4 3,3′,4,4′- 3,5-Diaminobenzoic 2-Hydroxy-Biphenyl- acid ethyl methacrylate tetracarboxylic (70) (200) dianhydride4,4′-Diamino- (100) diphenyl ether (30) 5 3,3′,4,4′- 2,4-Diaminophenol2-Hydroxy- Biphenyl- (95) ethyl methacrylate tetracarboxylicBis(3-amino- (200) dianhydride propyl)tetramethyl (100) disiloxane (5) 63,3′,4,4′- 4,4′-Diamino-3,3- 2-Hydroxy- Biphenyl- dihydroxybiphenylethyl methacrylate tetracarboxylic (50) (200) dianhydride 4,4′-Diamino-(100) diphenyl ether (50)

TABLE 2 Compositions of photosensitive polyimide precursors Aciddianhydride Diamine OH component Example (molar ratio) (molar ratio)(molar ratio) 7 4,4′- 3,5-Diaminobenzoic 2-Hydroxy- Oxydiphthalic acidethyl methacrylate dianhydride (50) (200) (100) 4,4′-Diamino- diphenylether (50) 8 4,4′- 3,5-Diaminobenzoic 2-Hydroxy- Oxydiphthalic acidethyl methacrylate dianhydride (70) (200) (100) 4,4′-Diamino- diphenylether (30) 9 4,4′- 2,4-Diaminophenol 2-Hydroxy- Oxydiphthalic (95) ethylmethacrylate dianhydride Bis(3-aminopropyl)- (200) (100) tetramethyldi-siloxane (5) 10 4,4′- 4,4′-Diamino-3,3- 2-Hydroxy- Oxydiphthalicdihydroxybiphenyl ethyl methacrylate dianhydride (50) (200) (100)4,4′-Diamino- diphenyl ether (50)

TABLE 3 Example Repeating unit (mol %) 3, 7

4, 8

TABLE 4 Ex- am- ple Repeating unit (mol %) 5, 9 

6, 10

In the structural formulas shown in Table 3 and Table 4, R is a grouprepresented by the following formula (20) in Examples 3 to 6 or a grouprepresented by the following formula (21) in Examples 7 to 10. Thenumbers in the patentheses in Tables 3 and 4 denote the percentage (mol%) of each kind of repeating units based on the total number of moles ofrepeating units in a molecule of the polyimide precursor.

In the same manner as in Example 1, each of the obtained polyimideprecursors was dissolved in a solvent, and a photosensitizer and aphotopolymerization assistant were added (a comonomer was further addedin Examples 6 and 10) thereto to prepare a photosensitive polyimideprecursor composition. A film was formed from this composition in thesame manner as described in Example 1, and the resolution, sensitivity,development time, elongation of the film, and adhesive properties of thefilm were investigated. The results obtained are shown in Table 5 andTable 6. In Table 5 and Table 6, the amount of each additive added per100 parts by weight of the photosensitive polyimide precursor is shownin the parentheses.

TABLE 5 Evaluation of characteristics of photosensitive polyimideprecursors Photopolymerization Characteristics Photosensitizer asistantComonomer Development Adhesive Example (parts by weight) (parts byweight) (parts by weight) Resolution Sensitivity time Elongationproperties 3 Michler's N-phenylglycine None Good Good Good Good Goodhetone (2) (1) 4 7-Diethylamino- 3,3′,4,4′- None Good Good Good GoodGood 4-methyl- Tetra(t-butyl- coumarin peroxycarbomyl- (2) benzophenone(2) 5 Benzanthrone 4-Diethylamino- None Good Good Good Good Good (0.5)ethylbenzoate (1) 6 2,6-Di(p-di- 2,6-Di(p- Tetraethylene Good Good GoodGood Good methylamino- azidobenzal)-4- glycol benzal)-4- carboxycyclo-dimethacrylate carboxycyclo- hexanone (5) hexanone (2) (2)

TABLE 6 Evaluation of characteristics of photosensitive polyimideprecursors Photopolymerization Characteristics Photosensitizer assistantComonomer Development Adhesive Example (parts by weight) (parts byweight) (parts by weight) Resolution Sensitivity time Elongationproperties 7 Michler's N-phenylglycine None Good Good Good Good Goodhetone (2) (1) 8 7-Diethylamino- 3,3′,4,4′- None Good Good Good GoodGood 4-methyl- Tetra(t-butyl- coumarin peroxycarbomyl- (2) benzophenone(2) 9 Benzanthrone 4-Diethylamino- None Good Good Good Good Good (0.5)ethylbenzoate (1) 10  2,6-Di(p-di- 2,6-Di(p- Tetraethylene Good GoodGood Good Good methylamino- azidobenzal)-4- glycol benzal)-4-carboxycyclo- dimethacrylate carboxycyclo- hexanone (5) hexanone (2) (2)

The film formation conditions and the evaluation conditions were thesame as those described in Example 1. The film thickness was adjusted to10 to 20 μm. The resolution was rated as good when a through-hole of 10μm was resolved. The sensitivity was rated as good when an exposure doseat which the film thickness after the development became one-half of thecoating thickness was 100 mJ/cm² or less. The development time was ratedgood when the development could be carried out within 1 minute with a2.38 wt % aqueous tetramethylammonium hydroxide solution as a developingsolution. The film elongation was rated as good when the elongation of afinally obtained polyimide film was 8% or more. The adhesive propertieswere rated good when no peeling was observed in pressure-sensitiveadhesive tape test (JIS D-0202) on the polyimide film on a silicon waferwhich had been finally obtained by curing by heating.

EXAMPLES 11 TO 12

Acid chlorides of tetracarboxylic acid diesters were synthesized in thesame manner as described in Example 1 except for using the aciddianhydride mixture and OH component and alcohol mixture listed in Table7. Polyimide precursors comprising the repeating units shown in Table 8were synthesized by adding the diamine mixture listed in Table 7 to asolution of each acid chloride, and reacting the diamine mixture withthe acid chloride in the same manner as described in Example 1. Theweight-average molecular weights of the obtained polyimide precursorswere 20,000 to 40,000.

TABLE 7 Compositions of photosensitive polyimide precursors Aciddianhydride Diamine OH component Example (molar ratio) (molar ratio)(molar ratio) 11 3,3′4,4′- 3,5-Diaminobenzoic 2-Hydroxy- Biphenyl- acidethyl methacrylate tetracarboxylic (50) (100) dianhydride 4,4′-Diamino-Ethanol (50) diphenyl ether (100) Pyromellitic (50) dianhydride (50) 124,4′- 3,5-Diaminobenzoic 2-Hydroxy- Oxydiphthalic acid ethylmethacrylate dianhydride (50) (100) (50) 4,4′-Diamino- EthanolPyromellitic diphenyl ether (100) dianhydride (50) (50)

TABLE 8 Example Repeating unit (mol %) 11, 12

As R in the structural formulas shown in Table 8, two kinds of groupsrepresented by the following formulas (22), respectively, are present ina molar ratio of 1:1 in the polyimide precursor of Example 11, and twokinds of groups represented by the following formulas (23),respectively, are present in a molar ratio of 1:1 in the polyimideprecursor of Example 12. The numbers in the patentheses in Table 8denote the percentage (mol %) of each kind of repeating units based onthe total number of moles of repeating units in a molecule of thepolyimide precursor.

In the same manner as in Example 1, each of the obtained polyimideprecursors was dissolved in a solvent, and a photosensitizer, aphotopolymerization assistant and a comonomer were added thereto toprepare a photosensitive polyimide precursor composition. A film wasformed from this composition in the same manner as described in Example1, and the resolution, sensitivity, development time, elongation of thefilm, and adhesive properties of the film were investigated. The resultsobtained are shown in Table 9. The film formation conditions, evaluationconditions and criterions for evaluation were the same as thosedescribed in Examples 3 to 10. Also in Table 9, the amount of eachadditive added per 100 parts by weight of the photosensitive polyimideprecursor is shown in the parentheses as in Table 5 and Table 6.

TABLE 9 Evaluation of characteristics of photosensitive polyimideprecursors Photopolymerization Characteristics Photosensitizer assistantComonomer Development Adhesive Example (parts by weight) (parts byweight) (parts by weight) Resolution Sensitivity time Elongationproperties 11 2,4- 1,3-Diphenyl- Tetraethylene Good Good Good Good GoodDiethylthio- 1,2,3-propane- glycol xanthone trione-2-(o- diacrylate (1)ethoxy- (8) carbonyl)oxime (3) 12 2,4- 1,3-Diphenyl- Tetraethylene GoodGood Good Good Good Dimethylthio- 1,2,3-propane- glycol xanthonetrione-2-(o- diacrylate (2) ethoxy- (8) carbonyl)oxime (3)

EXAMPLES 13 TO 27

Acid chlorides of tetracarboxylic acid diesters were synthesized in thesame manner as described in Example 1 except for using the aciddianhydride and one or two OH components and/or alcohols listed inTables 10 to 12. Polyimide precursors comprising the repeating unitsshown in Table 13 were synthesized by reacting each acid chloride withthe diamines listed in Tables 10 to 12 under the same reactionconditions as described in Example 1. The weight-average molecularweights of the obtained polyimide precursors were 10,000 to 40,000.

TABLE 10 Compositions of photosensitive polyimide precursors Aciddianhydride Diamine OH component Example (molar ratio) (molar ratio)(molar ratio) 13 3,3′,4,4′- 3,5-Diaminobenzoic 2-Hydroxy- Biphenyl- acidethyl methacrylate tetracarboxylic (70) (100) dianhydride 4,4′-Diamino-Methanol (100) diphenyl ether (100) (30) 14 3,3′,4,4′-3,5-Diaminobenzoic 2-Hydroxy- Biphenyl- acid ethyl methacrylatetetracarboxylic (70) (140) dianhydride 4,4′-Diamino- n-Butanol (100)diphenyl ether (60) (30) 15 3,3′,4,4′ 4,4′-Diamino- 2-Hydroxy- Biphenyl-diphenylether-2- ethyl methacrylate tetracarboxylic carboxylic acid(200) dianhydride (70) (100) 4,4′-Diamino- diphenyl ether (30) 163,3′,4,4′- 4,4′-Diamino- 2-Hydroxy- Biphenyl- diphenylmethane- ethylmethacrylate tetracarboxylic 3,3′-dicarboxylic (200) dianhydride acid(100) (70) 4,4′-Diamino- diphenyl ether (30) 17 3,3′,4,4′-3,5-Diaminobenzoic 2-Hydroxy- Biphenyl- acid ethyl methacrylatetetracarboxylic (70) (200) dianhydride 4,4′-Diamino- (100) diphenylether (30)

TABLE 11 Compositions of photosensitive polyimide precursors Aciddianhydride Diamine OH component Example (molar ratio) (molar ratio)(molar ratio) 18 4,4′- 3,5-Diaminobenzoic 2-Hydroxy- Oxydiphthalic acidethyl methacrylate dianhydride (70) (100) (100) 4,4′-Diamino- Methanoldiphenyl ether (100) (30) 19 4,4′- 3,5-Diaminobenzoic 2-Hydroxy-Oxydiphthalic acid ethyl methacrylate dianhydride (70) (140) (100)4,4′-Diamino- n-Butanol diphenyl ether (60) (30) 20 4,4′- 4,4′-Diamino-2-Hydroxy- Oxydiphthalic diphenylether-2- ethyl methacrylate dianhydridecarboxylic acid (200) (100) (70) 4,4′-Diamino- diphenyl ether (30) 214,4′- 4,4′-Diamino- 2-Hydroxy- Oxydiphthalic diphenylmethane- ethylmethacrylate dianhydride 3,3′-dicarboxylic (200) (100) acid (70)4,4′-Diamino- diphenyl ether (30) 22 4,4′- 3,5-Diamino- 2-Hydroxy-Oxydiphthalic benzoic acid ethyl methacrylate dianhydride (70) (200)(100) 4,4′-Diamino- diphenyl ether (30)

TABLE 12 Compositions of photosensitive polyimide precursors Aciddianhydride Diamine OH component Example (molar ratio) (molar ratio)(molar ratio) 23 3,3′-4,4′- 3,5-Diaminobenzoic 2-Hydroxy-Diphenylsulfone- acid ethyl methacrylate tetracarboxylic (70) (100)dianhydride 4,4′-Diamino- Methanol (100) diphenyl ether (100) (30) 243,3′-4,4′- 3,5-Diaminobenzoic 2-Hydroxy- Diphenylsulfone- acid ethylmethacrylate tetracarboxylic (70) (140) dianhydride 4,4′-Diamino-n-Butanol (100) diphenyl ether (60) (30) 25 3,3′-4,4′- 4,4′-Diamino-2-Hydroxy- Diphenylsulfone- diphenylether-2- ethyl methacrylatetetracarboxylic carboxylic acid (200) dianhydride (70) (100)4,4′-Diamino- diphenyl ether (30) 26 3,3′-4,4′- 4,4′-Diamino- 2-Hydroxy-Diphenylsulfone- diphenylmethane- ethyl methacrylate tetracarboxylic3,3′-dicarboxylic (200) dianhydride acid (100) (70) 4,4′-Diamino-diphenyl ether (30) 27 3,3′-4,4′- 3,5-Diamino- 2-Hydroxy-Diphenylsulfone- benzoic acid ethyl methacrylate tetracarboxylic (70)(200) dianhydride 4,4′-Diamino- (100) diphenyl ether (30)

TABLE 13 Ex- am- ple Repeating unit (molar ratio %) 13, 18, 23

14, 19, 24

15, 20, 25

16, 21, 26

17, 22, 27

In the structural formulas shown in Table 13, R is a group representedby the following formula (28) in Examples 13 to 17, a group representedby the following formula (29) in Examples 18 to 22, or a grouprepresented by the following formula (30) in Examples 23 to 27:

In the structural formulas shown in Table 13, R³ is a group representedby the following formula (31) in Examples 13 to 16, 18 to 21 and 22 to27, or a group represented by the following formula (32) in Examples 17,22 and 27:

In the same manner as in Example 1, each of the obtained polyimideprecursors was dissolved in a solvent, and a photosensitizer, aphotopolymerization assistant and a comonomer were added thereto toprepare a photosensitive polyimide precursor composition. A film wasformed from this composition in the same manner as described in Example1, and the resolution, sensitivity, development time, elongation of thefilm, and adhesive properties of the film were investigated. The resultsobtained are shown in Tables 14 to 16. The film formation conditions,evaluation conditions and criterions for evaluation were the same asthose described in Examples 3 to 10. In the Tables, the numbers in theparentheses denote the amount of each additive added per 100 parts byweight of the photosensitive polyimide precursor.

TABLE 14 Evaluation of characteristics of photosensitive polyimideprecursor compositions Photopolymerization CharacteristicsPhotosensitizer assistant Comonomer Development Adhesive Example (partsby weight) (parts by weight) (parts by weight) Resolution Sensitivitytime Elongation properties 13 Michler's N-phenylglycine TetraethyleneGood Good Good Good Good ketone (2) glycol (2) diacrylate (10) 147-Diethyl- 3,3′,4,4′-Tetra- Tetraethylene Good Good Good Good Goodamino-4- (t-butylperoxy- glycol methyl- carbonyl)benzo- diacrylatecoumarin phenone (10) (2) (2) 15 Benzanthrone 4-Diethylamino-Tetraethylene Good Good Good Good Good (0.5) ethyl benzoate glycol (1)diacrylate (10) 16 7-Diethyl- 1,3-Diphenyl-1,2,3- Tetraethylene GoodGood Good Good Good amino-4- propanetrione-2-(o- glycol methyl-ethoxycarbonyl)- diacrylate coumarin oxime (10) (1) (3) 17 7-Diethyl-1,3-Diphenyl-1,2,3- Tetraethylene Good Good Good Good Good amino-4-propanetrione-2-(o- glycol methyl- ethoxycarbonyl)- diacrylate coumarinoxime (10) (3) (3)

TABLE 15 Evaluation of characteristics of photosensitive polyimideprecursor compositions Photopolymerization CharacteristicsPhotosensitizer assistant Comonomer Development Adhesive Example (partsby weight) (parts by weight) (parts by weight) Resolution Sensitivitytime Elongation properties 18 Michler's N-phenylglycine TetraethyleneGood Good Good Good Good ketone (2) glycol (2) diacrylate (10) 197-Diethyl- 3,3′,4,4′-Tetra- Tetraethylene Good Good Good Good Goodamino-4- (t-butylperoxy- glycol methyl- carbonyl)benzo- diacrylatecoumarin phenone (10) (2) (2) 20 Benzanthrone 4-Diethylamino-Tetraethylene Good Good Good Good Good (0.5) ethyl benzoate glycol (1)diacrylate (10) 21 7-Diethyl- 1,3-Diphenyl-1,2,3- Tetraethylene GoodGood Good Good Good amino-4- propanetrione-2-(o- glycol methyl-ethoxycarbonyl)- diacrylate coumarin oxime (10) (1) (3) 22 7-Diethyl-1,3-Diphenyl-1,2,3- Tetraethylene Good Good Good Good Good amino-4-propanetrione-2-(o- glycol methyl- ethoxycarbonyl)- diacrylate coumarinoxime (10) (3) (3)

TABLE 16 Evaluation of characteristics of photosensitive polyimideprecursor compositions Photopolymerization CharacteristicsPhotosensitizer assistant Comonomer Development Adhesive Example (partsby weight) (parts by weight) (parts by weight) Resolution Sensitivitytime Elongation properties 23 Michler's N-phenylglycine TetraethyleneGood Good Good Good Good ketone (2) glycol (2) diacrylate (10) 247-Diethyl- 3,3′,4,4′-Tetra- Tetraethylene Good Good Good Good Goodamino-4- (t-butylperoxy- glycol methyl- carbonyl)benzo- diacrylatecoumarin phenone (10) (2) (2) 25 Benzanthrone 4-Diethylamino-Tetraethylene Good Good Good Good Good (0.5) ethyl benzoate glycol (1)diacrylate (10) 26 7-Diethyl- 1,3-Diphenyl-1,2,3- Tetraethylene GoodGood Good Good Good amino-4- propanetrione-2-(o- glycol methyl-ethoxycarbonyl)- diacrylate coumarin oxime (10) (1) (3) 27 7-Diethyl-1,3-Diphenyl-1,2,3- Tetraethylene Good Good Good Good Good amino-4-propanetrione-2-(o- glycol methyl- ethoxycarbonyl)- diacrylate coumarinoxime (10) (3) (3)

EXAMPLE 28

A. Synthesis of a Poly(amic acid) Ester

A poly(amic acid) ester comprising the same repeating units of thefollowing formula (16) as those of the poly(amic acid) ester synthesizedin Example 1 was synthesized in the same manner as described in Example1:

Synthesis of a Siloxane-containing Poly(amic acid)

In a 100-ml four-necked flask were placed 10.00 g (0.0234 mol) of1,3-bis(3,4-dicarboxyphenylic anhydride)-1,1,3,3-tetramethyldisiloxane(SXDA) and 29 ml of NMP, and 5.82 g (0.0234 mol) of1,3-bis(3-aminopropyl)tetramethyldisiloxane was added with stirring at25° C. When the stirring was continued, a transparent solution wasobtained in 2 hours. This solution was diluted with 50 ml of NMP and thedilution was poured into 1 liter of water, after which the polymerprecipitated was collected by filtration, washed twice with water andthen dried in vacuo to obtain 13 g of a poly(amic acid) comprisingrepeating units of the formula (33) shown below. The weight-averagemolecular weight of the poly(amic acid) was measured by GPC and found tobe 20,000 in terms of polystyrene.

C. Preparation of a Polyimide Precursor Composition

In 15.0 g of γ-butyrolactone were dissolved 9 g of the poly(amic acid)ester obtained in step A and 1 g of the poly(amic acid) obtained in stepB, and then 100 mg of3,5-bis(4-diethylaminobenzylidene)-1-methyl-4-azacyclohexanone and 200mg of 4-diethylaminoethyl benzoate. The resulting solution was filteredthrough a filter with a pore size of 5 μm under pressure to obtain aphotosensitive polyimide precursor composition in the form of asolution.

D. Evaluation of the Viscosity Stability of Varnish

The obtained photosensitive polyimide precursor composition solution(varnish) was placed in a brown bottle and its viscosity was measured at25° C. and found to be 4.50 mPa.s. When the varnish was then stored atroom temperature for 1 week, the varnish was not gelatinized and itsviscosity at 25° C. was 4.60 mPa.s, namely, it was stable without asignificant change.

E. Evaluation of a Polyimide Film

Using the obtained solution (varnish), a polyimide film of 10 μm thickwas formed on a silicon wafer in the same manner as in Example 1. Whenthe adhesive properties of the polyimide film was measured bypressure-sensitive adhesive tape test (JIS D-0202), no peeling wasobserved. In addition, when the silicon wafer having the polyimide filmformed thereon was subjected to PCT treatment (125° C., 2.3 atmospheres)for 500 hours and the adhesive properties were measured again, nopeeling was observed at all. On the other hand, the polyimide film waspeeled from the silcon wafer and the elongation of the film was measuredand found to be as good as 9%. The dependence of the film thicknessafter development on exposure dose was measured to find that thesensitivity was 80 mJ/cm2 when the sensitivity was defined as anexposure dose at which the film thickness after development becameone-half of the coating thickness.

When a polyimide film of 2 to 3 μm thick was formed in the same manneras above and its infrared absorption spectrum was measured, there wereobserved an absorption due to imide group at 1780 cm−1 and an absorptiondue to carboxyl group at 2800 to 3600 cm−1.

F. Formation of a Resin Pattern

The polyimide precursor composition prepared in step C was coated,exposed to light, developed and then rinsed in the same manner asdescribed in step E, except that in the exposure, the coating film wasclosely covered with a photomask patterned with stripes of 10 μm wide.Thus, there was obtained a relief pattern of 10 μm wide made ofsemi-cured polyimide precursor and having sharp edge faces. This patternwas heat-treated in the same manner as in the above-mentioned polyimidefilm formation to obtain a resin pattern made of polyimide, with highprecision.

EXAMPLE 29

A. Synthesis of a Poly(amic acid) Ester

In the same manner as in Example 2, 20 g of a poly(amic acid) estercomprising the same repeating units of the following formula (18) asthose of the poly(amic acid) ester synthesized in Example 2 wasobtained. The weight-average molecular weight of this polymer wasmeasured by GPC and found to be 39,000 in terms of polystyrene.

B. Synthesis of a Siloxane-containing Poly(amic acid)

In a 100-ml four-necked flask were placed 10.00 g (0.0234 mol) of SXDAand 29 ml of NMP, and 8.85 g (0.0234 mol) of1,3-bis(m-aminophenoxymethyl)tetra-methyldisiloxane was added withstirring at 25° C. When the stirring was continued, a transparentsolution was obtained in 2 hours. This solution was diluted with 50 mlof NMP and the dilution was poured into 1 liter of water, after whichthe polymer precipitated was collected by filtration, washed twice withwater and then dried in vacuo to obtain 13 g of a poly(amic acid)comprising repeating units of the formula (34) shown below. Theweight-average molecular weight of the poly(amic acid) was measured byGPC and found to be 20,000 in terms of polystyrene.

C. Preparation of a Polyimide Precursor Composition

In 15.0 g of γ-butyrolactone were dissolved 9 g of the poly(amic acid)ester obtained in step A and 1 g of the siloxane-containing poly(amicacid) obtained in step B, and then 100 mg of Michler's ketone and 200 mgof 1,3-diphenyl-1,2,3-propanetrione-2-(o-ethoxy-carbonyl)oxime. Theresulting solution was filtered through a filter with a pore size of 5μm under pressure to obtain a photosensitive polyimide precursorcomposition in the form of a solution.

D. Evaluation of the Viscosity Stability of Varnish

The obtained photosensitive polyimide precursor composition solution(varnish) was placed in a brown bottle and its viscosity was measured at25° C. and found to be 4.10 mPa.s. When the varnish was then stored atroom temperature for 1 week, the varnish was not gelatinized and itsviscosity at 25° C. was 4.20 mPa.s, namely, it was stable without asignificant change.

E. Evaluation of a Polyimide Film

Using the obtained solution (varnish), a polyimide film of 10 μm thickwas formed on a silicon wafer in the same manner as in Example 1. Whenthe polyimide film was evaluated in the same manner as described inExample 28, it exhibited the same high adhesive properties as thoseattained in Example 28, and a better elongation of 10%. The sensitivitywas 90 mJ/cm².

When a polyimide film of 2 to 3 μm thick was formed in the same manneras above and its infrared absorption spectrumμm was measured, there wereobserved an absorption due to imide group at 1785 cm⁻¹ and an absorptiondue to carboxyl group at 2800 to 3600 cm⁻¹.

F. Formation of a Resin Pattern

The polyimide precursor composition prepared in step C was coated,exposed, developed and then rinsed in the same manner as described instep E, except that in the exposure to light, the coating film wasclosely covered with a photomask patterned with stripes of 10 μm wide.Thus, there was obtained a relief pattern of 10 μm wide made ofsemi-cured polyimide precursor and having sharp edge faces. This patternwas heat-treated in the same manner as in the above-mentioned polyimidefilm formation to obtain a resin pattern made of polyimide, with highprecision.

EXAMPLES 30 TO 39

Acid chlorides of tetracarboxylic acid diesters were synthesized in thesame manner as described in Example 1, step A except for using the aciddianhydride and one or two OH components listed in Table 17 and Table18. Poly(amic acid) esters were synthesized by reacting each acidchloride with the one or two diamines listed in Tables 17 and 18. Theweight-average molecular weights of the obtained poly(amic acid) esterswere 20,000 to 40,000.

TABLE 17 Compositions of photosensitive polyimide precursors Aciddianhydride Diamine OH component Example (molar ratio) (molar ratio)(molar ratio) 30 3,3′,4,4′- 3,5-Diaminobenzoic 2-Hydroxy- Biphenyltetra-acid ethyl methacrylate carboxylic (50) (200) dianhydride 4,4′-Diamino-(100) diphenyl ether (50) 31 3,3′-4,4′- 3,5-Diaminobenzoic 2-Hydroxy-Biphenyltetra- acid ethyl methacrylate carboxylic (70) (240) dianhydride4,4′-Diamino- (100) diphenyl ether (30) 32 3,3′-4,4′- 3,5-Diaminobenzoic2-Hydroxy- Biphenyltetra- acid ethyl methacrylate carboxylic (50) (100)dianhydride 4,4′-Diamino- n-Butanol (100) diphenyl ether (100) (50) 333,3′-4,4′- 3,5-Diaminobenzoic 2-Hydroxy- Biphenyltetra- acid ethylmethacrylate carboxylic (70) (100) dianhydride 4,4′-Diamino- n-Butanol(100) diphenyl ether (100) (30) 34 3,3′-4,4′- 4,4′-Diamino-3,3′-2-Hydroxy- Biphenyltetra- dihydroxybiphenyl ethyl methacrylatecarboxylic (100) (200) dianhydride (100)

TABLE 18 Compositions of photosensitive polyimide precursors Aciddianhydride Diamine OH component Example (molar ratio) (molar ratio)(molar ratio) 35 4,4′- 3,5-Diaminobenzoic 2-Hydroxy- Oxydiphthalic acidethyl methacrylate dianhydride (50) (200) (100) 4,4′-Diamino- diphenylether (50) 36 4,4′- 3,5-Diaminobenzoic 2-Hydroxy- Oxydiphthalic acidethyl methacrylate dianhydride (70) (200) (100) 4,4′-Diamino- diphenylether (30) 37 4,4′- 3,5-Diaminobenzoic 2-Hydroxy- Oxydiphthalic acidethyl methacrylate dianhydride (50) (100) (100) 4,4′-Diamino- n-Butanoldiphenyl ether (100) (50) 38 4,4′- 3,5-Diaminobenzoic 2-Hydroxy-Oxydiphthalic acid ethyl methacrylate dianhydride (70) (100) (100)4,4′-Diamino- n-Butanol diphenyl ether (100) (30) 39 4,4′-4,4′-Diamino-3,3′- 2-Hydroxy- Oxydiphthalic dihydroxybiphenyl ethylmethacrylate dianhydride (100) (200) (100)

Siloxane-containing poly(amic acid)s comprising the repeating unitsshown in Table 21 were synthesized in the same manner as described inExample 28, step B except for using the one or two acid di-anhydridesand one or two diamines listed in Table 19 and Table 20. Theweight-average molecular weights of the obtained poly(amic acid)s were10,000 to 40,000.

TABLE 19 Compositions of poly(amic acid)s Acid dianhydride DiamineExample (molar ratio) (molar ratio) 30, 35 1,3-Bis(3,4-dicarboxy-1,3-Bis(3-aminopropyl)- phenylic anhydride)- tetramethyldisiloxane1,1,3,3-tetramethyl- (100) disiloxane (100) 31 1,3-Bis(3,4-dicarboxy-1,3-Bis(3-aminopropyl)- phenylic anhydride)- tetramethyldisiloxane1,1,3,3-tetramethyl- (100) disiloxane (50) 3,3′4,4′-Biphenyltetra-carboxylic dianhydride (50) 32 1,3-Bis(3,4-dicarboxy-1,3-Bis(3-aminopropyl)- phenylic anhydride)- tetramethyldisiloxane1,1,3,3-tetramethyl- (100) disiloxane 4,4′-Diaminodiphenyl (50) ether3,3′,4,4′-Biphenyltetra- (50) carboxylic dianhydride (50) 33, 381,3-Bis(3,4-dicarboxy- 4,4′-Diaminodiphenyl phenylic anhydride)- ether1,1,3,3-tetramethyl- (100) disiloxane (100) 34 3,3′,4,4′-Biphenyltetra-1,3-Bis(3-aminophenoxy- carboxylic dianhydride methyl)tetramethyl- (100)disiloxane (100)

TABLE 20 Compositions of poly(amic acid)s Acid dianhydride DiamineExample (molar ratio) (molar ratio) 36 1,3-Bis(3,4-dicarboxy-1,3-Bis(3-aminopropyl)- phenylic anhydride)- tetramethyldisiloxane1,1,3,3-tetramethyl- (100) disiloxane (50) 4,4′-Oxydiphthalicdianhydride (50) 37 1,3-Bis(3,4-dicarboxy- 1,3-Bis(3-aminopropyl)-phenylic anhydride)- tetramethyldisiloxane 1,1,3,3-tetramethyl- (50)disiloxane 4,4′-Diaminodiphenyl (50) ether 4,4′-Oxydiphthalic (50)dianhydride (50) 39 4,4′-Oxydiphthalic 1,3-Bis(3-aminopropyl)-dianhydride tetramethyldisiloxane (100) (100)

TABLE 21 Ex- am- ple Repeating unit (molar ratio %) 30, 35

31

32

33, 38

34

36

37

39

The numbers in the patentheses in Table 21 denote the percentage (mol %)of each kind of repeating units based on the total number of moles ofrepeating units in a molecule of the poly(amic acid). In Table 21, R¹⁴through R¹⁷ represent the following structures:

In the same manner as in Example 28, each of the obtained poly(amicacid) esters and each of the obtained siloxane-containing poly(amicacid)s were dissolved in a solvent, and a photosensitizer, aphoto-polymerization assistant and a comonomer were added thereto toprepare a photosensitive polyimide precursor composition. The stabilityof the thus obtained compositions was evaluated in the same manner asdescribed in Example 28 to find that all the compositions were good instability like the composition obtained in Example 28. A film was formedfrom each composition in the same manner as described in Example 28 andthe resolution, sensitivity, development time, and elongation of thefilm were investigated. Table 22 and Table 23 show the additives used ineach Example and characteristics of the film obtained in the Example.The amount of each additive added is expressed in parts by weight in theparentheses.

TABLE 22 Evaluation of characteristics of photosensitive polyimideprecursor compositions Siloxane- Poly- contain- (amic ing poly- acid)(amic ester acid) Photopolymerization Comonomer Characteristics Exam-(parts by (parts by Photosensitizer assistant (parts by DevelopmentAdhesive ple weight) weight) (parts by weight) (parts by weight) weight)Resolution Sensitivity time Elongation properties 30 (10) (90) Michler'sN-phenyl- None Good Good Good Good Good ketone glycine (2) (2) 31  (5)(95) 7-Diethyl- 3,3′,4,4′- None Good Good Good Good Good amino-4-Tetra(t- methyl- butylperoxy- coumarin carbonyl)- (2) benzophenone (2)32  (3) (97) Benzanthrone 4-Diethyl- None Good Good Good Good Good (0.5)aminoethyl benzoate (1) 33 (10) (90) 7-Diethyl- 1,3-Diphenyl- None GoodGood Good Good Good amino-4- 1,2,3-propane- methyl- trione-2-(o-coumarin ethoxy- (1) carbonyl)oxime (3) 34  (1) (99) 7-Diethyl-1,3-Diphenyl- Tetra- Good Good Good Good Good amino-4- 1,2,3-propane-ethylene methyl- trione-2-(o- glycol di- coumarin ethoxy- acrylate (3)carbonyl)oxime (10) (3)

TABLE 23 Evaluation of characteristics of photosensitive polyimideprecursor compositions Siloxane- Poly- contain- (amic ing poly- acid)(amic ester acid) Photopolymerization Comonomer Characteristics Exam-(parts by (parts by Photosensitizer assistant (parts by DevelopmentAdhesive ple weight) weight) (parts by weight) (parts by weight) weight)Resolution Sensitivity time Elongation properties 35 (10) (90) Michler'sN-phenyl- None Good Good Good Good Good ketone glycine (2) (2) 36  (5)(95) 7-Diethyl- 3,3′,4,4′- None Good Good Good Good Good amino-4-Tetra(t- methyl- butylperoxy- coumarin carbonyl)- (2) benzophenone (2)37  (3) (97) Benzanthrone 4-Diethyl- None Good Good Good Good Good (0.5)aminoethyl benzoate (1) 38 (10) (90) 7-Diethyl- 1,3-Diphenyl- None GoodGood Good Good Good amino-4- 1,2,3-propane- methyl- trione-2-(o-coumarin ethoxy- (1) carbonyl)oxime (3) 39  (1) (99) 7-Diethyl-1,3-Diphenyl- Tetra- Good Good Good Good Good amino-4- 1,2,3-propane-ethylene methyl- trione-2-(o- glycol di- coumarin ethoxy- acrylate (3)carbonyl)oxime (10) (3)

The film formation conditions and the evaluation conditions were thesame as those described in Example 1, and the film thickness wasadjusted to 10 to 20 μm. However, the adhesive properties were rated asgood when no peeling was observed when pressure-sensitive adhesive tapetest (JIS D-0202) was carried out after PCT treatment (125° C., 2.3atmospheres) for 500 hours.

Comparative Example 1

A photosensitive polyimide precursor was synthesized in the same manneras in Example 1 of JP-B 5-67026, and using this precursor, aphotosensitive polyimide precursor composition was prepared in the samemanner as described in Example 1 of the present specification. When acoating film was formed from the composition, exposed to light through aphotomask, and then developed with the same developing solution asdescribed in Example 1 of the present specification, no pattern could beformed because both the exposed portion and the non-exposed portion werenot soluble in the developing solution at all. Therefore, a pattern wasobtained by carrying out development with the organic solvent(N-methylpyrrolidone) described in Example 1 of JP-B 5-67026, but theresolution was so poor that only through-holes of 30 μm or more could beresolved.

Comparative Example 2

In the same manner as in Example of JP-B 63-31939, the poly(amic acid)listed as No. 1 in Table 1 of this reference was synthesized, and usingthis poly(amic acid), a photosensitive polyimide precursor compositionwas prepared in the same manner as described in Example 1 of the presentspecification. When a coating film was formed from the composition,exposed to light through a photomask, and then developed with the samedeveloping solution as described in Example 1 of the presentspecification, no pattern could be formed because both the exposedportion and the non-exposed portion were dissolved in the developingsolution.

Therefore, a coating film was formed in the same manner as above,exposed to light, developed with the developer composed of organicsolvents (a mixed solvent consisting of 4 volumes ofN-methyl-2-pyrrolidone and 1 volume of ethanol) described in Example 1of JP-B 61-31939, and then rinsed with ethanol to obtain a pattern, butthe resolution was so poor that only through-holes of 40 μm or morecould be resolved.

Comparative Example 3

A photosensitive polyimide precursor was synthesized in the same manneras in Example 1 of JP-A 6-258835, and using this precursor, aphotosensitive polyimide precursor composition was prepared in the samemanner as described in Example 1 of the present specification. When afilm was formed from the composition, exposed, and then developed (theexposed portion were removed in the present comparative example) withthe same developing solution as described in Example 1 of the presentspecification, the sensitivity was so low that no pattern of 10 μm thickcould be formed unless the exposure dose was 1,000 mJ/cm2 or more.Moreover, the development time (the time of immersion in the developingsolution) was 5 minutes or more.

As described above in detail, the polyimide precursor of the presentinvention is soluble in an alkaline aqueous solution. When the polyimideprecursor is a photosensitive polyimide precursor havingphoto-sensitivity imparted by introduction of photosensitive groups, thepolyimide precursor can be developed not with an organic solvent butwith an alkaline aqueous solution. Therefore, when a resin pattern isformed using a photosensitive material or a photosensitive polyimideprecursor composition, which contains the polyimide precursor of thepresent invention, various problems in the employment of an organicsolvent, such as undesirable influences on the health of workers, etc.can be avoided. In addition, when the polyimide precursor of the presentinvention is used in a protective film (e.g. the surface coating film ofa semiconductor device), the interlaminar insulating film of a thin-filmmultilayer circuit board, or the like, the swelling of exposed portionduring development, labor required for treating a waste fluid, etc. canbe reduced.

Furthermore, of the polyimide precursors of the present invention,photosensitive polyimide precursors having photosensitivity imparted byintroduction of photosensitive groups are highly sensitive and requireonly a short development time, so that a process for forming a resistpattern using a photosensitive material or a photosensitive polyimideprecursor composition, which contains the photosensitive polyimideprecursor is satisfactorily suitable as a practical production process.

What is claimed is:
 1. A process for forming a resin pattern, whichcomprises: forming a film of a negative-working photo-sensitivepolyimide precursor composition on a substrate; exposing the film tolight through a mask having a predetermined pattern; and developing theexposed film using an alkaline aqueous solution; and wherein thepolyimide precursor is contained in an amount of 100 parts by weight,together with 0.1 to 50 parts by weight of photosensitizer, and 0.1 to50 parts by weight of a photopolymerization auxiliary agent; wherein thepolyimide precursor composition comprises a polyimide precursor havingrepeating units of the formula:

wherein R¹ is a tetravalent organic group having 4 or more carbon atoms;R² is a trivalent or tetravalent organic group containing one or morearomatic rings; R³ is a monovalent photosensitive organic group; A is amonovalent group showing acidity; and n is an integer of 1 or
 2. 2. Aprocess according to claim 1, wherein the polyimide precursor has aweight-average molecular weight of 10,000 to 200,000, and R³ isrepresented by the formula:

wherein R⁵, R⁶, and R⁷ are independently a hydrogen atom, an alkylgroup, a phenyl group, a vinyl group, or a propenyl group; and R⁸ is adivalent organic group.
 3. A process according to claim 2, wherein R³ isrepresented by the formula:


4. A process according to claim 1, wherein A is at least one groupselected from the group consisting of a sulfonic acid group, a sulfinicacid group, a carboxylic acid group, and a hydroxyl group.
 5. A processaccording to claim 1, wherein A is a carboxylic acid group.
 6. A processaccording to claim 1, wherein

is a group of the formula:


7. A process for forming a resin pattern, which comprises forming a filmof a negative-working photosensitive polyimide precursor composition ona substrate, exposing the film to light through a mask having apredetermined pattern, and developing the exposed film using an alkalineaqueous solution; wherein the polyimide precursor is contained in anamount of 100 parts by weight, together with 0.1 to 50 parts by weightof photosensitizer, and 0.1 to 50 parts by weight of aphotopolymerization auxiliary agent; wherein the polyimide precursorcomposition has repeating units of formula:

wherein R¹ is a tetravalent organic group having 4 or more carbon atoms;R² is a trivalent or tetravalent organic group containing one or morearomatic rings; R³ is a monovalent photosensitive organic group; A is amonovalent group showing acidity; and n is an integer of 1 or 2; andwherein the polyimide precursor further has repeating units of theformula:

 wherein R¹ is a tetravalent organic group having 4 or more carbonatoms; R² is a trivalent or tetravalent organic group having one or morearomatic rings; R³ is a monovalent photosensitive organic group; R⁴ is adivalent organic group containing one or more aromatic rings or siliconatoms; the number of repeating units of the formula (21-1) being 10 ormore, and the number of repeating units of the formula (21-2) being 90or less, when a total of repeating units of the formulae (21-1) and(21-2) is 100.